Conventionally, there were the following problems (1)-(3) in case of multipath route communication to improve the communication when the traffic is discarded in a network due to an insufficient link band width on a route in the network.
(1) It was difficult to dynamically adopt a multipath route according to the reception situation of the traffic of each terminal.
(2) When adopting the multipath route, it was difficult to select an identical copy (full mirroring) and a partial copy (partial mirroring), a flow base division, a random division and so on in a split position according to the situation of the network.
(3) It was difficult to adopt the dynamic optimum design so as to minimize the cost imposed on the network by taking a multipath route.
Regarding the problem (1), as a generally used multipath route generation technique, there are “OSPF ECMP technique” (Open Shortest Path First Equal Cost Multi Path), “MPLS Traffic Engineering technique” (Multi Protocol Label Switching Traffic Engineering) and so on.
In “the OSPF ECMP technique”, because a multipath route is statically generated according to network topology and a link cost in the network, a plurality of routes are generated in a portion of the multipath route of the identical cost in the network. However, it is difficult to set a plurality of routes in an optional position, and the route is selected in a flow base by the Hash function in the split position of the multipath. Therefore, it is difficult to control according to the reception situation of the traffic of each terminal.
On the other hand, in “MPLS Traffic Engineering technique”, a multipath route is dynamically generated according to the network topology, the link cost, and a traffic amount flowing through the link. However, the multipath can not be generated from a node on the way of the network and it is difficult to control according to the reception situation of the traffic of each terminal.
Therefore, it is demanded that multipath route is dynamically generated according to the reception situation of the traffic flow of each terminal to improve the traffic reception performance of the terminal.
Regarding the problem (2), a plurality of routes are prepared previously at the edge of the network, as shown in JP 2004-312153A (Patent Literature 1), and JP 2007-94681 A (Patent Literature 2). It should be noted that the edge of the network is an entrance of the network.
In JP 2004-312153 A (Patent Literature 1), a method is disclosed in which in the environment that optical edges are connected to both of an IP network (Internet Protocol Network) and a photonic network, two routes are set previously, and communication is switched to the side of the photonic network when the a predetermined quantity of traffic flows through the IP network. In this method, communication is switched to the photonic network when detecting a large amount of traffic, because enough performance can not be attained in a large capacity communication of the IP network. In this way, because this method carries out a simple switching control between the networks, a function of branching in an optional position in the network and copy and division functions such as the identical copy, the partial copy, the flow base division and the random division can not be attained.
On the other hand, in JP 2007-94681A (Patent Literature 2), a method is disclosed in which a redundant route candidacy (a route which is not allocated with a resource) is provided previously when a plurality of routes in the network are provided, and a resource is allocated once more at a necessary time. In this method, the redundant path is not allocated with a resource previously, and a plurality of transmission servers shares a route. In this way, because this method is related to a resource sharing method of a redundant path, a function of branching in an optional position of the network and the functions such as the identical copy, the partial copy, the flow base division and the random division can not be attained.
Moreover, in the problem (2), as shown in JP 2007-208953A (Patent Literature 3), a technique is known in which a plurality of multicast paths are dynamically set in the edge of the network (entrance of the network). In JP 2007-208953A (Patent Literature 3), a method of generating a plurality of multicast trees is disclosed. This method uses a hash function in use after the generation. However, a destination for the traffic to be transferred to according to the contents and a route branched from a transmission source (edge) of the multicast are determined by use of the hash function that regarding the route of the multicast. In this way, because this method is to make the multicast tree itself redundant, there is no function of branching in an optional position in the network and of a copy and division such as an identical copy, a partial copy, a flow base division and a random division.
Therefore, when adopting the multipath route, a technique is demanded in which either of the identical copy, the partial copy, the flow base division, the random division and so on is dynamically selected in the split position according to the situation of the network, so as to improve in the traffic reception performance of the terminal.
Regarding the problem (3), because a load is imposed on the network due to the traffic subjected to the multicast communication when the multicast communication is branched from an optional route, it is required to maximize the reception performance of the terminal while suppressing the load as much as possible. However, as mentioned above, because there is not a function of branching in the optional position in the network in a conventional method, there is no technique for maximizing reception performance of the terminal.